diff --git a/lib/savon/soap/request.rb b/lib/savon/soap/request.rb
index 3cecef8c..b8905bc3 100644
--- a/lib/savon/soap/request.rb
+++ b/lib/savon/soap/request.rb
@@ -40,7 +40,7 @@ def configure(http)
         http.url = soap.endpoint
         http.body = soap.to_xml
         http.headers["Content-Type"] = ContentType[soap.version]
-        http.headers["Content-Length"] = soap.to_xml.length.to_s
+        http.headers["Content-Length"] = soap.to_xml.bytesize.to_s
         http
       end